1. Field of the Invention
This invention relates to a rangefinder for cameras and, more specifically, to an arrangement of the mounting terminals and light-emission elements of a light-emission-element package constituting a light-emission block in a light-emission-type multipoint rangefinder.
2. Related Art Statement
Conventionally, in a so-called multipoint automatic focusing device for performing range finding on a plurality of points of the type whose light-emitting and light-receiving sections are arranged horizontally with respect to the front side of an associated camera, a plurality of LED elements constituting the light-emission device have generally been arranged horizontally on the light-emission side, and, on the light-reception side, a plurality of PSD elements constituting the light-reception device have likewise been arranged horizontally, in order to avoid a so-called middle clearing.
FIGS. 5, 6 and 7 are a front view, a side view and a bottom view, respectively, of a conventional light-reception PSD package of a unitary type, in which a PSD element 51 is arranged in a package 50 and, further, mounting terminals 52 and 53 are arranged above and below the PSD element. When the light-reception device is thus formed by a single PSD element, the device has a large noise component, resulting in a low accuracy in range finding. FIGS. 8, 9 and 10 are a front view, a side view and a bottom view, respectively, of another conventional light-reception PSD package, in which a number of light-reception PSD elements 56 corresponding to the number of points in range finding (three in this case) are arranged so as to allow range finding to be performed from short to long distances. With this arrangement, the accuracy in range finding can be improved, each light-reception element functioning as an independent one. In the drawings, reference numerals 57 and 58 indicate mounting terminals. However, when, as in the case of FIG. 8, the PSD device consists of a number of PSD elements, the light-receiving package 55 has a larger lateral dimension as compared to the case of FIG. 5. This obviously constitutes a commensurate barrier to reducing the camera size.
Further, when, as in the case of FIG. 8, the PSD device consists of a number of PSD elements, the centers of the PSD elements are spaced apart from each other by a larger distance, which inevitably makes it necessary for the light-emission angle of the beam on the light-emission side to be very large. For example, when the PSD device shown in FIG. 8 is used in a compact camera with a zoomer (f 110 mm.about.f 38 mm), the light-emission angle must naturally be large, so that, although the light-emission beam can be held within the finder field in the case of a short focus (f 38 mm), it cannot be held within the finder field in the case of a long focus (f 110 mm).
In view of this, an oblique arrangement of PSD elements as shown, for example, in FIG. 11, has been proposed. FIGS. 11, 12 and 13 are a front view, a side view and a bottom view, respectively, of the outer configuration of a PSD package 60, in which three light-reception elements 62 are arranged obliquely with respect to a package 61. In the drawings, numerals 63 and 64 indicate mounting terminals. With this PSD device 60, constructed as described above, it is possible to miniaturize the package 61. However, the oblique arrangement of the PSD elements 62 naturally makes it necessary for the light-emission LED elements also to be arranged obliquely.
FIGS. 14A and 14B are perspective views showing an arrangement of the components of the range finding section of a multipoint rangefinder and respectively using such light-emission LED and light-reception PSD devices as described above. FIGS. 15A and 15B show a front view of the arrangement shown FIGS. 14A and 14B respectively. Referring to the drawings, in a light-emission LED device 65, three LED elements 67 are arranged laterally side by side inside a package 66, with mounting terminals 68 and 69 extending perpendicular to the dimension along which the three LED elements 67 are arranged. As for the light-reception device, which is the same as the light-reception PSD device 60 of FIG. 11, the package 61 itself is arranged in an erect position as shown in FIGS. 14A and 15A, so that the three light-reception elements 62 are arranged obliquely. Thus, with the LED device 65, it is necessary to arrange its package 66 in a tilted position with respect to an axis J (FIG. 15A) connecting it with the PSD device 60, and the three LED elements 67 are obliquely positioned as shown in FIG. 15A. As shown in FIGS. 14A and 15A and 14B and 15B, a light-emission lens 70 and a light-reception lens 71 are respectively arranged in front of the LED device 65 and PSD device 60, respectively.
FIG. 16 is a front view of a camera in which the light-emission LED elements are arranged perpendicular to the dimension along which the mounting terminals extend. As shown in the drawing, a lens frame unit 91 and a zoom driving unit 87 are arranged in the central section of the camera body, and, in the upper section of the camera body, a finder unit 88 and an electronic flash unit 89 are arranged. A body unit 90 is arranged in the camera section on the right hand side. The light-emission LED device 65 and the light-reception photo detector 92, which constitute the multipoint rangefinder, are mounted on a mounting substrate 93, and arranged longitudinally on the left-hand side of the lens frame unit 91. In the drawing, dimension X4 indicates the base length of the multipoint rangefinder, and dimension X7 indicates the height of the camera equipped with this multipoint rangefinder.
When, in the arrangement shown in FIGS. 14A and 15A, the elements 67 of the light-emission LED device 65 are arranged perpendicular to or along the same dimension as the mounting terminals 68 and 69, the vertical dimension X0 of the mounting terminals 68 and 69 is rather large, with the result that a reduction of the vertical dimension of the camera housing is considerably restricted, thus constituting a barrier to a reduction in camera size. Further, when actually mounting the LED device 65 in a camera, the LED device is attached to a mounting substrate 80a, as shown in FIG. 17, before it is installed in the camera. As a result, the diagonal dimension X2 of the mounting substrate 80a is the vertical dimension it actually occupies in the camera. Thus, it obviously further restricts a reduction in terms of camera size.
FIG. 18 is a front view of a camera with its front housing section removed, showing the LED device 65 as provided therein together with other components. In this case, the LED device 65 is installed in the camera together with a PSD device 60' installed in the same way as shown in FIG. 14B, except that the mounting terminals of the PSD device 60' extend along a dimension different from that of the light-reception PSD device 60. Before being installed in the camera, the light-emission LED device 65 is attached to the mounting substrate 80a in the manner shown in FIG. 17 and, in this condition, mounted in the section "a" of the camera. The light-reception PSD device 60' is attached to a mounting substrate 80b and mounted in the section "b" of the camera. The mounting terminals 63' and 64' of the light-reception PSD device 60' extend laterally as indicated by the broken lines in FIG. 11. In the central section of the camera, a lens frame unit 82 and a zoom driving unit 83 are arranged, and, in the upper section of the camera, a finder unit 84 and an electronic flash unit 85 are arranged. These components are supported by the camera body 86. In this conventional camera, constructed as described above, the dimension X4 of the height of the camera housing 81 is rather great because of the unutilized space due to the diagonal dimension X2 of the mounting substrate 80a of the LED device 65.
Also, in the construction shown in FIG. 16, the height X7 of the camera is rather great due to the extending terminals of the light-emission package 65.